How many kinds of visceral afferents?
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure*; D019899:Paracrine Communication; D012684:Sensory Thresholds / Q000502:physiology; D017833:Visceral Afferents / Q000378:metabolism / Q000648:ultrastructure*